Pressure Loss Modelling in a Water-Cooled Hollow-Shaft Rotor for an Automotive Traction Motor

An accurate evaluation of the pressure loss in a rotor cooling system is necessary to predict the overall cooling efficiency of the electrical machines. This paper presents and discusses the numerical simulations of the rotational friction loss factor in a hollow-shaft, where the effects of the rotation rate as well as the numerical divisions of the shaft have been accounted for. On this basis, a Reynolds Stress Transport (RST) model is employed to provide a better understanding of the rotating effects on the flow patterns. From the CFD simulations, it is concluded that the shaft rotation has two opposite effects on the pressure loss, boosting or diminishing above the level of the stationary condition.